COMPUTER

NOTESWritten by

Navan ChauhanClass-4th

Birla Vidya Niketan sector 4 New Delhi-110017

Contents•History of computers•1st Generation•2nd Generation•3rd Generation•4th Generation•5th Generation•What is a computer •Input devices•Output devices•CPU•ALU•CU•Memory

History of computersThe first use of the word "computer" was recorded in 1613, referring to a person who carried out calculations, or computations, and the word continued with the same meaning until the middle of the 20th century. From the end of the 19th century the word began to take on its more familiar meaning, a machine that carries out computations.

Generation of computer

Model of 1st generation

First Generation (1941-1956)World War gave rise to numerous developments and started off the computer age. Electronic Numerical Integrator and Computer (ENIAC) was produced by a partnershp between University of Pennsylvannia and the US government. It consisted of 18,000 vacuum tubes and 7000 resistors. It was developed by John Presper Eckert and John W. Mauchly and was a general purpose computer. "Von Neumann designed the Electronic Discrete Variable Automatic Computer (EDVAC) in 1945 with a memory to hold both a stored program as well as data." Von Neumann's computer allowed for all the computer functions to be controlled by a single source.Then in 1951 came the Universal Automatic Computer(UNIVAC I), designed by Remington rand and collectively owned by US census bureau and General Electric. UNIVAC amazingly predicted the winner of 1952, presidential elections, Dwight D. Eisenhower.In first generation computers, the operating instructions or programs were specifically built for the task for which computer was manufactured. The Machine language was the only way to tell these machines to perform the operations. There was great difficulty to program these computers ,and more when there were some malfunctions. First Generation computers used Vacuum tubes and magnetic drums(for data storage).

Model of 2nd generation computers

Second Generation (1956-1963)

The invention of Transistors marked the start of the second generation. These transistors took place of the vacuum tubes used in the first generation computers. First large scale machines were made using these technologies to meet the requirements of atomic energy laboratories. One of the other benefits to the programming group was that the second generation replaced Machine language with the assembly language. Even though complex in itself Assemly language was much easier than the binary code.Second generation computers also started showing the characteristics of modern day computers with utilities such as printers, disk storage and operating systems. Many financial information was processed using these computers.In Second Generation computers, the instructions(program) could be stored inside the computer's memory. High-level languages such as COBOL (Common Business-Oriented Language) and FORTRAN (Formula Translator) were used, and they are still used for some applications nowdays.

Model of 3rd generation

Third Generation (1964-1971)

Although transistors were great deal of improvement over the vacuum tubes, they generated heat and damaged the sensitive areas of the computer. The Intergreated Circuit(IC) was invented in 1958 by Jack Kilby. It combined electronic components onto a small silicon disc, made from quartz. More advancement made possible the fitings of even more components on a small chip or a semi conductor. Also in third generation computers, the operating systems allowed the machines to run many different applications. These applications were monitored and coordinated by the computer's memory.

Model of 4th generation

Fourth Generation (1971-Present)Fourth Generation computers are the modern day computers. The Size started to go down with the improvement in the integrated circuits. Very Large Scale(VLSI) and Ultra Large scale(ULSI) ensured that millions of components could be fit into a small chip. It reduced the size and price of the computers at the same time increasing power, efficiency and reliability. "The Intel 4004 chip, developed in 1971, took the integrated circuit one step further by locating all the components of a computer (central processing unit, memory, and input and output controls) on a minuscule chip."Due to the reduction of cost and the availability of the computers power at a small place allowed everyday user to benefit. First came the minicomputers, which offered users different applications, most famous of these the word processors and spreadsheets, which could be used by non-technical users. Video game systems like Atari 2600 generated the interest of general populace in the computers. In 1981, IBM introduced personal computers for home and office use. "The number of personal computers in use more than doubled from 2 million in 1981 to 5.5 million in 1982. Ten years later, 65 million PCs were being used." Computer size kept getting reduced during the years. It went down from Desktop to laptops to Palmtops. Machintosh introduced Graphic User Interface in which the users didn't' have to type instructions but could use Mouse for the purpose. The continued improvement allowed the networking of computers for the sharing of data. Local Area Networks(LAN) and Wide Area Network(WAN), were potential benefits, in that they could be implemented in corporations and everybody could share data over it. Soon the internet and World Wide Web appeared on the computer scene and form ended the Hi-Tech revolution of 90's.

Model of 5th generation

Fifth Generation (Present and Beyond)Fifth generations computers are only in the minds of advance research scientiets and being tested out in the laboratories. These computers will be under Artifical Intelligence(AI), They will be able to take commands in a audio visual way and carry out instructions. Many of the operations which requires low human intelligence will be perfomed by these computers.Parallel Processing is coming and showing the possibiliy that the power of many CPU's can be used side by side, and computers will be more powerful than thoes under central processing. Advances in Super Conductor technology will greatly improve the speed of information traffic. Future looks bright for the computers.

DEFINITION OF COMPUTER : COMPUTER IS AN ELECTRONIC DEVICE THAT IS DESIGNED TO WORK WITH INFORMATION.THE TERM ‘COMPUTER IS DERIVED FROM THE LATIN TERM ‘COMPUTARE’, THIS MEANS TO CALCULATE.COMPUTER CAN NOT DO ANYTHING WITHOUT A PROGRAM. IT REPRESENTS THE DECIMAL NUMBERS THROUGH A STRING OF BINARY DIGITS. THE WORD 'COMPUTER‘ USUALLY REFERS TO THE CENTER PROCESSOR UNIT PLUS INTERNAL MEMORY.

What is a computer?

The input unit is formed by the input devices attached to the computer. Ex - Keyboard, Microphone etc. An input unit takes the input & converts it into binary form so that it can be understood by the computer.

Keyboard

This is most commonly used device which acts as input device. Its structure is like typewriter. It contains no. of keys which have some specific ASCII values. Like ‘A’ has ASCII value 65. When this is pressed , it is converted into 65 & this 65 is sent to CPU in the form of Binary language (i.e. 1000001). Then operations are done on this data. Keyboard was invented by Qwerty

Mouse

This is a pointing device which contains a roller in its base. When the mouse is moved on any surface, the pointer on the screen is also moved. It contains a potentiometer coupled with the roller. This potentiometer senses the motion of mouse & convert it into digital value. A mouse may contain two or three buttons. Now a day's optical mouse are very popular. Mouse was invented by Douglas Englebert

BAR CODE READER

It is a device which is used to read the code from the products which are usually in the form of Bars. It contains a light sensitive detector which identifies the values of the bars on the product & converts them into numeric code. These Bar readers are used in Shopping malls in a very large scale.

DIGITAL CAMERA

As the name specifies, these camera stores the data digitally, which then can be stored in the computer & can be stored for a long time. But it has very limited storage capacity. These are very popular because of less expensive photographs & Speed.

LIGHT PEN

It is a pointing device which contains a photocell mounted at its tip. It senses the light from the screen when it becomes closer to the screen, & generates a pulse. So for identifying a particular location on the screen these light pens are very useful. But this is not in very much use these days.

Scanner

The scanner is an input device like the photocopier machine which makes the electronic copy of the picture or document which can be further edited.

MIC's or MICROPHONES

A microphone (colloquially called a mic or mike; both pronounced /ˈmark/)[1] is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. Microphones are used in many applications such as telephones, tape recorders, karaoke systems, hearing aids, motion picture production, live and recorded audio engineering, FRS radios, megaphones, in radio and television broadcasting and in computers for recording voice, speech recognition, VoIP, and for non-acoustic purposes such as ultrasonic checking or knock sensors.

The devices which are used to display the data to the user either in the form of hard copy or soft copy are called output devices.

These devices gives the hard copy of the output. These are in different types.Impact - Have mechanical contact in between paper & printing headNon Impact - No mechanical contact between paper & printing head

PRINTER

IMPACT :Line Printers - print line wise (E.g. Drum Printer)Character Printer - print character wise (E.g. Daisy Printer)

NON IMPACT -Electromagnet PrintersThermal PrintersElectrostatic PrintersInkjet PrintersLaser Printers

Speakers receive the sound in the form of electric current from the sound card & convert it to sound format. These are used for listening music, chatting , seminars for presentations etc

SPEAKERS

VDU [Visual Display Unit

This is also called monitor. It is used to get the data in the form of soft copy. Their functioning is exactly similar to the television. It contains a CRT which emits the electrons to trace a regular pattern of horizontal lines on the screen.

LCD (Liquid Crystal Display)

These screens are used in laptops & notebook sized PCs. A special type of liquid is sandwiched between two plates. The top plate is clear & bottom plate is reflective. The molecules in these liquids are normally aligned & the computer signals are used to align these molecules.

The CPU is Also Known As: processor, computer processor, microprocessor, central processor, "the brains of the computer"

The CPU is the control center for a computer. It guides, directs & governs its performance. It is the brain of the computer.

CPU CONTAINS :

1. Arithmetic & Logical Unit

2. Control Unit

ALU (Arithmetic Logic Unit)

An Arithmetic and Logical Unit (ALU) is a digital circuit that performs arithmetic and logical operations. The ALU is a fundamental building block of the central processing unit (CPU) of a computer. ALU is a combination of Arithmetic Unit & Logical Unit. Arithmetic Unit performs all the arithmetic operations like addition , subtraction , multiplication & division performed on the operands.

For example : a + b a - b a * B a / b

CU (Control Unit)

2. It sends control signals until the required operations are done properly by ALU & memory.3. It gets program instructions from memory & executes them one after another.4. It controls the flow of data from input device to memory & from memory to output devices.

Control Unit is most important part which controls all the internal as well as external functions in the computer. THE MAIN FUNCTIONS PERFORMED BY THE CONTROL UNIT ARE :1. It controls & guides the interpretation , flow & manipulation of all data & information.

Memory

PRIMARY MEMORY SECONDARY MEMORY

Primary Memory consist of RAM (random access memory) and ROM (read only memory). In this type of primary memory data is not stored permanently, it is stored temporarily . After getting off data is erased from the memory of computer. “These are considered as short term memory”

Secondary memory (or secondary storage) is the slowest and cheapest form of memory. It cannot be processed directly by the CPU. It must first be copied into primary storage (also known as RAM ). Secondary memory devices include magnetic disks like hard drives and floppy disks; optical disks such as CDs and CD ROMs; and magnetic tapes, which were the first forms of secondary memory.

The working place in computer where all data is stored is called memory. There are small cells called bit. In these cell data is stored in the form of 0 & 1. Its unit is bytes. A memory cell may be defined as a device which can store a symbol selected from a set of symbols.

CPURegister

Cache

Level-1

Level-2

RAM

Physical RAM Virtual Memory